1. Field of the Invention
This invention relates to a camera module, and more specifically to a camera module that can be used in small-sized electronic apparatuses such as digital cameras, camera-equipped cellular phones and the like.
2. Description of the Related Art
A camera module having a function of displacing a lens unit in a direction of an optical axis of the lens unit is used in relatively small-sized digital cameras, camera-equipped cellular phones and the like. This function is used for providing an autofocus function and/or zoom function and the like, and is achieved by an interaction between a magnetic field generated by an electrical current flowing in a coil and a magnetic field generated by a yoke and magnets provided on the yoke.
Such a camera module includes a barrel which holds the lens unit, a holder which houses the barrel therein, and a pair of leaf springs for supporting the holder so that the holder is displaceable in a direction of an optical axis of the lens unit. Further, the camera module also includes lead wires (that is, both end portions of a wire of the coil) for supplying an electrical current to the coil provided around the holder which is displaceable in the optical axis direction.
FIG. 3 is an exploded perspective view of an autofocus actuator assembly 100 used in a conventional camera module for displacing a lens unit (not shown) in a direction of an optical axis thereof. It is to be noted that an imaging element (not shown) is provided below a base 111 of the actuator assembly 100.
A holder 108 that houses a barrel (not shown) holding the lens unit is provided in a space between a cover 101 and the base 111 so that the holder 108 is displaceable in a direction of an optical axis of the lens unit together with the lens unit.
A ring-shaped inner annular portion 104b of an upper leaf spring 104 and a ring-shaped inner annular portion 110b of a lower leaf spring 110 are attached to the upper and lower cylindrical end portions of the holder 108, respectively, using an adhesive. Further, an outer annular portion 104a of the upper leaf spring 104 is attached to a top surface of a yoke 105 and an outer annular portion 110a of the lower leaf spring 110 is provided on a lower end of the yoke 105, respectively. Furthermore, on the upper surface of the inner annular portion 104b of the upper spring 104 which is attached to the upper cylindrical end portion of the holder 108, a stopper denoted by the reference numeral 102 is attached using an adhesive.
Three bridge portions 104c are coupled between the outer annular portion 104a and the inner annular portion 104b of the upper leaf spring 104. As is the same with the upper leaf spring 104, three bridge portions 110c are coupled between the outer annular portion 110a and the inner annular portion 110b of the upper leaf spring 110. By resilient deformation of the respective three bridge portions 104c and 110c, the holder 108 can be displaced in a direction of an optical axis of the lens unit.
A plurality of magnets 106 are provided on the yoke 105 so as to produce a magnetic field. The yoke 105 has an axial bore 105a for receiving the holder 108. Further, a coil 107 is provided around an outer periphery of the holder 108 so that the coil 7 is disposed in the magnetic field produced by the magnets and the yoke 105 in a state that the holder 108 is received in the axial bore 105a. By supplying a current to the coil 107 to generate a magnetic field, the holder 108 can be displaced in a direction of an optical axis of the lens unit by a driving force generated by the interaction of the magnetic fields. In this regard, it is to be noted that a component donated by the reference numeral 109 is a ring-shaped plate provided between the lower leaf spring 110 and the lower end of the yoke 105.
A flexible printed circuit board 103 for supplying an electrical current to the coil 107 is provided below the outer annular portion 110a of the lower leaf spring 110, and two lead wires (that is, both end portions of a wire of the coil) 103a, 103b are extended from the coil 107 through notches 110d, 110d formed on the inner periphery of the inner annular portion 110b of the lower leaf spring 110 (see FIG. 4). Tip ends of the lead wires 103a, 103b are connected to pads 103c, 103d of the flexible printed circuit board 103, respectively. In more details, these lead wires 103a, 103b are arranged below the bridge portions 110c so as to extend through a predetermined space below the bottom surfaces of the bridge portions 110c. As described above, the outer annular portion 110a of the lower spring 110 is attached to the yoke 105 through the plate 109, and the yoke 105 is electrically connected to a cover of a substrate (not shown) on which the camera module is to be mounted to thereby provide a ground therebetween.
It is to be noted that an actuator assembly similar to the actuator assembly 100 described above is disclosed in JP-A-No. 2004-280031.
As described above, the lead wires 103a, 103b are arranged below the bridge portions 110c so as to extend through a predetermined space below the bottom surfaces of the bridge portions 110c. In the camera module having the above structure, in the event that the electronic apparatus equipped with the camera module is dropped by accident and thus the holder 108 is abruptly displaced due to the shock, there is a case that the bridge portion 110c is largely deformed toward the corresponding lead wire to make severely contact with the lead wire to thereby damage an insulation coating of the lead wire. If such a damage of the insulation coating of the lead wire occurs and thereby the bridge portion 110c makes direct contact with a conductor of the lead wire, momentary shunt is caused between the lead wire and the ground through the lower leaf spring 110 and the yoke 105.
In the conventional camera module described above, in order to prevent such undesirable damage of the lead wire, regions of the bottom surfaces of the bridge portions 110c which correspond to the lead wires 103a, 103b are coated with an insulating resin such as silicone resin so that the insulation coating is not damaged by the deformed bridge portion 110c even in the case where the bridge portion makes severely contact with the lead wire.
In the method mentioned above, it is necessary to carry out an application of the silicone resin or the like onto the bottom surfaces of the bridge portions 110c in the manufacturing process of the camera module. However, since the width of each bridge portion is extremely narrow, the application of the resin must be carried out carefully. Therefore, there is a problem in that it takes a relatively long time in manufacturing the camera module. Further, a cost of the synthetic resin must be included in a manufacturing cost of the camera module, thus leading to an increased manufacturing cost of the camera module.